Process for the production of metals and alloys with very small contents of carbon



Feb. 2, 1937. G. ANDERSEN 2,069,469

PROCESS FOR THE PRODUCTION OF METALS AND ALLOYS WITH VERY SMALL CONTENTSOF CARBON Filed Dec. 22, 1933 (Hinder-so Patented Feb. 2, 193 7 2 UNITEDSTATES PATENT OFFICE Gustav Andersen, Copenhagen, Denmark ApplicationDecember 22, 1933, Serial No. 703,641

3 Claims.

This invention relates to a process for the production of metals andalloys with very small contents of carbon.

It is known that very important dimculties are met in the production ofmetals and alloys with very small contents of carbon, for instancechromium and manganese with very small contents of carbon as well astheir alloys, especially chromeor manganese-iron and steel alloys, dueto the fact that the said metals possess a great aflinity for carbon.

As a rule, the production of stainless steel, for instance, is realizedby using an alloy of chromium and iron, having a high chromium contentbut a low content of carbon, which alloy is added to the finished,melted steel.

Obviously, the indirect producing processes are very expensive, on theone hand due to difficulty of making such a chrome-iron alloy and on theother hand due to the losses arising from the melting together, andaccordingly it is better to use a direct process in which a directreduction of the alloy metals in the main metal is effected. In one ofsaid processes, bricks of chromite thoroughly ground are added, withferro-silicon or with a silicon containing reducing means, to melted andoverheated iron. The additional metal in the alloy is reduced in thebath of metal which is thoroughly stirred, a direct production of thealloy being thus effected, having the desired analysis, for instance astainless steel.

Very often a process is used in which no carbon-containing reducingmeans are used, and in which electrodes are used that are not allowed tocome into direct contact with the metal for reduction purposes, but itis clear that an alloy will be obtained having a variable and too high acontent of carbon. This process is especially suitable for high carboncontents. Apparently, in the above process, the carbon which is absorbedcomes from the raw materials, ore, ferrosilicon or slag. I

Analyses made with the ore used show that it has a carbon content of0.04 to 0.10% or even more. In a further process ferrosilicon andlimestone are used. Carbon is likely to be found in the foreign matters,plant fibers, leaves, earth, etc. getting mixed with the ore in thecourse of transportation or in ore bunkers.

An output of more than 60 to 70% of the Norway December 31, 1932 Beforea charge of correctly determined quan- 10 titles of ore, ferro-siliconor other silicon containing reduction means and limestone is put into anoverheated main-metal bath, which only contains a very small quantity ofcarbon, it is submitted to a pre-treatment by heating it to atemperature of 1000 to 1100 C. i. e. without melting it in a stronglyoxidizing flame, in order to burn out the carbon which is in the charge,and to have the limestone transformed into caustic lime.

process is practiced. Fig. 1 is a vertical section taken on the line I-Iof Fig. 2 of a furnace adapted to the purpose. Fig. 2 is a horizontalview of the same furnace.

The drawing shows diagrammatically how the The charge is ground to asuitable size of grain (like grits or even smaller) thoroughly stirredup and loaded through a feeder i in a thin layer (about 4" thick) over acontinuously rotating heating platform 2 where it will meet thecombustion gases from a hot strongly oxidizing flame 3 incountercurrent, the furnace being for instance of the type described inthe U. S. A. patent application Ser. No. 703,640 of 1933.

After the treatment, the hot charge is discharged at 4 into closed ironboxes 5 for cooling and storing purposes.

If the combustion gases are to be used again in the process for heatingpurposes, the carbon dioxide is previously separated, for instance bydirecting the gases which are conducted up through the feeder i througha caustic potash filter 6 or similar product before the gases areconducted back by a fan I to the furnace at the point where theoxidizing flame 3 is produced.

This purification by which sulphur is also eliminated, is very importantif good results are to be obtained. Similarly it is necessary to use astrong oxidizing flame.

The charge which has been freed from carbon,

may be added directly to melted metal for a final high-temperaturetreatment. for instance to an iron bath having a very low carboncontent. The determined quantity of charge is poured into the iron bathdirectly from the closed box I in which it is stored in order to preventits oxidizatlon. Thus a metal having the precise, desired analysis isobtained.

Having thus described my invention what I claim is:

1. A process for the production of metals and alloys with a very smallcontent of carbon, by direct reduction of ore with silicon-containingreduction means on an over-heated metal bath with a very small contentof carbon, the said method including the use 01 a charge consisting ofore, limestone and silicon-containing reduction means, submitted, beforebeing charged into the main metal bath, to a pre-treatment byheatmaterial in a closed chamber and protecting the 1 said materialagainst contamination.

GUSTAV ANDERSEN.

